<!doctype html>
<html>
<head>
<meta charset="utf-8">
<title>了解css选择器</title>
<link href="style2.css" rel="stylesheet" type="text/css">
</head>

<body>
	<div>111</div>
	<div id="red">222</div>
	<div class="blue">333</div>
</body>
</html>
